Portion of a display screen with a graphical user interface



The FIGURE is a front view of a portion of a display screen with a graphical user interface showing the new design.

The dashed lines showing text and images form no part of the claimed design. Said dashed lines, dashed image, and text are presented only for environmental purposes. 

CLAIM The ornamental design for portion of a display screen with a graphical user interface, as shown and described. 